Dzogchen Ponlop

‘From the Buddhist point of view, when we refer to karma, we are not talking about fate but about a situation in which our actions from the past carry a certain weight and power to affect our present lives. We do have a blueprint, but it is one in which our past karma and our present karma both carry a certain percentage of the power. For example, there might be a particular situation in which our past karma carries fifty percent of the weight. This would mean that there is space – room for present conditions to arise and affect the current situation – for our present karma also to exert half of the total influence on that situation. These two together – past and present karma – constitute one hundred percent of our karma, or the totality of the causal elements that are present in any given situation.
From this perspective, our previous karma is like the seed of a beautiful flower. This seed has the potential to grow and produce a beautiful blossom. However, if we were to leave this flower seed on a table for a hundred years, then it would not produce any result. In order for the seed to produce its potential result, a number of supporting conditions must come together, for example, proper soil, proper temperatures, and sufficient water and sunshine. When these supporting conditions are present at the same time, the seed produces its result, which is a flower.’ (Wild Awakening)

I find it difficult to explain karma convincingly, so I am always glad to find passages where skilled teachers can lay it out in a simple manner like this.